Russia's Kommersant newspaper said Iranian Defence Minister Mostafa Mohammad Najjar will seek to get Russia to deliver the systems during his visit to Moscow, though the paper said Moscow was extremely wary of selling the systems to Tehran.

Kommersant said an $800 million contract for five S-300 systems had already been signed between Iran and Russia, but the paper cited a source in the Russian weapons industry saying that Moscow had not yet made a decision on whether to deliver them.

An Iranian lawmaker said last year that deliveries had already begun and some Russian media have reported that Russia is fulfilling a S-300 contract with Iran.

Russia is building Iran's first nuclear power plant in the southern port city of Bushehr, and says it will start up the reactor at the plant this year.

In October, Russia's Foreign Ministry denied media speculation that Moscow would sell the medium-range S-300 system, saying it had no intention of selling weapons to "troubled regions".

The most advanced version of the S-300 system can track targets and fire at aircraft 120 km (75 miles) away. It is known in the West as the SA-20.